LaF_3纳米晶体中Sm^(3+)/Eu^(3+)能量传递效应的光谱学特性（英文）

Spectroscopic Properties of Energy Transfer Effect in Sm^(3+)/Eu^(3+)Doped LaF_3 Nanocrystals

采用水热合成法,在较低的温度下制备了分散性,均匀性良好的LaF_3:Sm^(3+),LaF_3:Eu^(3+)和LaF_3:Sm^(3+)/Eu^(3+)纳米晶体样品。通过X射线衍射(XRD),透射电子显微镜(TEM)和光致发光(PL)等手段,分别对Sm^(3+)/Eu^(3+)单掺和共掺LaF_3纳米晶体的物相,表面形貌,晶粒尺寸和荧光特性进行了表征。XRD和TEM检测结果显示,所制备的LaF_3纳米晶体呈六方晶体相,平均粒径在40 nm左右。当采用波长为442 nm的He-Cd连续激光器激发Sm^(3+)/Eu^(3+)共掺LaF3样品中的Sm^(3+)时,在样品发射光谱中观测到了Eu^(3+)的特征荧光发射谱线,实现了Sm^(3+)向Eu^(3+)的能量传递。采用光谱学研究方法讨论了能量传递的机理和效率。结果表明,能量传递过程是Sm^(3+)的~4G_(5/2)激发态与Eu^(3+)的~5D_1和~5D_0激发态之间的交叉驰豫所致,并且随着Eu^(3+)的掺杂浓度的增大,共掺LaF_3:Sm^(3+)/Eu^(3+)样品的发射谱中的Eu^(3+)的特征荧光发射强度也随之增强,这说明增加受主Eu^(3+)的掺杂浓度能够有效地提高Sm^(3+)→Eu^(3+)能量传递的效率。

The samples of LaF3：Sm^3＋,LaF3：Er^3＋and LaF3：Sm^3＋ /Eu^3＋ nanocrystals with high quality mono-disperse and uniform sizes were synthesized with hydro thermal method.The crystallographic phase,surface morphology,crystalline sizes and fluorescence properties of Sm^3＋ /Eu^3＋ sole- and co-doped nanocrystals were characterized with X-ray powder diffraction（XRD）,transmission electron microscopy（TEM） and photoluminescence（PL） spectroscopic technique,respectively.The results of XRD and TEM show that the microstructure of the nanocrystals is hexagonal,with the average size about 40 nm.Using 442 nm He-Cd continuous wave（CW） laser to pump the Sm^3＋ ions doped in the LaF3：Sm^3＋/Eu^3＋nanocrystals,the typical fluorescence emissions originating from the Eu^3＋ions were observed in the emission spectra,and that the energy transfer from Sm^3＋ ions to Eu^3＋ ions was completed.The mechanism and efficiency of the energy transfer from Sm^3＋ ions to Eu^3＋ ions were investigated and discussed systematically based on the spectroscopic method.It is shown that the energy transfer of Sm^3＋ →Er^3＋ is attributed to the cross-relaxation between the excited state^4G（5/2） of Sm^3＋ ion and the ^5D1 and ^5D0 states of Eu^3＋ ion.Meanwhile,the intensities of the characteristic fluorescence emissions of Eu^3＋ ions become stronger and stronger with the increase of the Eu^3＋ doping concentration,which suggest that the efficiency of energy transfer from Sm^3＋ ions to Eu^3＋ ions can be effectively improved by increasing the doping concentration of Eu^3＋ acceptor.